The VAT policy has also been very unusual in how far they've pushed it along the Laffer curve in one go. 20% of the entire end cost!! That already seems to have reduced participation by 1.9% in the last year - despite the 'stickiness' of school education.(previous discussion on variability of private school participation notwithstanding)
The NI change was a 1.2% increase and reduced threshold - so the biggest percentage impact will be for employees earning £9000 (the old threshold) who will cost an extra 6.5% in tax. For an average £35k salary, the NI change has increased the cost of employing someone by 2.6% (due to the threshold change as well as % increase)
Anecdotally, people are saying that has made a difference to hiring levels, but it's not clear yet. For numbers, what I found is that: in February to April 2025, the estimated UK employment rate increased 0.1 percentage points to 75.1%, the UK unemployment rate increased 0.2 percentage points to 4.6%, and the UK economic inactivity rate decreased 0.2 percentage points to 21.3% compared with November 2024 to January 2025. So not really showing high enough levels of change to affect tax take from the NI rise yet - although it will take a while to feed through.
It would be interesting to see a breakdown of employment changes by salary over the next year, to see whether there are job losses at lower salaries (where the proportional cost increase is more). That could easily change the profitability of the NI change - since low income workers are much, much more likely to get UC if they lose their jobs, which increases the cost to the government. Eg if the 0.2 increase in unemployment is for low earners who will have the income replaced through UC... but the 0.2 increase in workforce participation is actually people increasing hours/SAHM re-entering the workforce due to COL pressure (who didn't get UC), that may still reduce the net tax take - even though the employment numbers balance.
I do suspect that if NI had increased by 15-20% (equivalent to the education VAT), it may have changed more noticeably already - as private school participation did. Although of course, the Laffer curve varies for each tax and each product.
I can't imagine them making a NI jump that big in one go though! It would rightly be condemned as reckless.